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Fix layout of spectrum_demo.py #8158

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Merged
NelleV merged 3 commits into from
Mar 6, 2017
Merged

Fix layout of spectrum_demo.py #8158

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ac09d60
Fix layout of spectrum_demo.py
DietBru Feb 26, 2017
b88f58c
Beautified spectrum_demo.py a little more.
DietBru Feb 28, 2017
f2bc54b
Added plot titles to spectrum_demo.py
DietBru Mar 1, 2017
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48 changes: 34 additions & 14 deletions examples/pylab_examples/spectrum_demo.py
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Original file line number Diff line number Diff line change
@@ -1,32 +1,52 @@
"""
========================
Spectrum Representations
========================

The plots show different spectrum representations of a sine signal with
additive noise. A (frequency) spectrum of a discrete-time signal is calculated
by utilizing the fast Fourier transform (FFT).
"""
import matplotlib.pyplot as plt
import numpy as np


np.random.seed(0)

dt = 0.01
Fs = 1/dt
dt = 0.01 # sampling interval
Fs = 1/dt # sampling frequency
t = np.arange(0, 10, dt)

# generate noise:
nse = np.random.randn(len(t))
r = np.exp(-t/0.05)

cnse = np.convolve(nse, r)*dt
cnse = cnse[:len(t)]
s = 0.1*np.sin(2*np.pi*t) + cnse

plt.subplot(3, 2, 1)
plt.plot(t, s)
s = 0.1*np.sin(4*np.pi*t) + cnse # the signal

fig, axes = plt.subplots(nrows=3, ncols=2, figsize=(7, 7))

# plot time signal:
axes[0, 0].set_title("Signal")
axes[0, 0].plot(t, s, color='C0')
axes[0, 0].set_xlabel("Time")
axes[0, 0].set_ylabel("Amplitude")

# plot different spectrum types:
axes[1, 0].set_title("Magnitude Spectrum")
axes[1, 0].magnitude_spectrum(s, Fs=Fs, color='C1')

plt.subplot(3, 2, 3)
plt.magnitude_spectrum(s, Fs=Fs)
axes[1, 1].set_title("Log. Magnitude Spectrum")
axes[1, 1].magnitude_spectrum(s, Fs=Fs, scale='dB', color='C1')

plt.subplot(3, 2, 4)
plt.magnitude_spectrum(s, Fs=Fs, scale='dB')
axes[2, 0].set_title("Phase Spectrum ")
axes[2, 0].phase_spectrum(s, Fs=Fs, color='C2')

plt.subplot(3, 2, 5)
plt.angle_spectrum(s, Fs=Fs)
axes[2, 1].set_title("Angle Spectrum")
axes[2, 1].angle_spectrum(s, Fs=Fs, color='C2')

plt.subplot(3, 2, 6)
plt.phase_spectrum(s, Fs=Fs)
axes[0, 1].remove() # don't display empty ax

fig.tight_layout()
plt.show()